Method of machining manganese steel.



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. WlNFIELD S. IPQYTTER, OF NEVJ YOEK, N. 2., ASSEGNOR ALLOY STEEL FOBGINCGMEAIT-Y, 0F WILMINGTON, DELAWARE, A CDEPOBJATION OF DELAWARE.

merger or MACHINING nauueunsn stunt.

v a citizen of. the United States, and a resident of New'York, boroughof Manhattan, in th nty of New York and State of New York, have made andinvented certain new and useful lmprovements in Methods of MachiningManganese Steel, of which the following is a specification.

My invention relates to methods of machining to finished form anddimensions such cast or wrought shapes of steels containing highpercentages of carbon and:

manganese as are non-machineable in the cold state, and has-particularlyfor its objectthe production of finished manganese steel shapes'in atough and strong condition suitable for service, and with accuratemachined surfaces as may be required.

manganese steel at ordinary temperatures cannot be machined by means ofhigh speed steel cutting tools, the'cutting edges of tools formed ofhigh speed steel are sufficiently strong to effect such machining attemperatures at the surface of intended cleavage in the manganese steelabove 300 C. or thereabout! As high speed steel of good quality, afterbeing suitably hardened does not lose its strength' or hardness untilreheated to'a temperature of about 600 to 650 (1., the, machining of themanganesesteel may not only be done at temperaturesapproximating 300 C.but at any higher temperature providing that the cutting edge of thehigh speed steel tool is not, during the operation, heated to above itssoftening'or annealing temperature of 600 to 650 C. In some cases themanganese steel may have a considerably higher temperature while beingmachined than the softening temperature of the high speed steel, andnotably sowhen the cutting is done by a number of rapidly moving cuttingedges as is the case of a rapidly turning milling cutter or barringwheel, or when, as in the case of a punch, the machining is accomplishedrapidly and when the machining tool remains in contact with the workfor'a time so short that the tool steel does not acquire the temperatureof the inachinedpiece.

The practice of my invention depends in some cases on the furtherdiscovery that-' when heat treated and toughened manganese t me to tern-Speciicaticnoi' Letters 'iatent.

I have found that whereas austenitic r s nted use; aog i me.

Application filed December 28,1911. Serial as. 668,458

peratures not above the criticalpoint lying approximately at420 GL5; ortma somewhat higher temperature" as, forexalnple, to 550 C. for ashorttimej 'the'toughLproperti-es of the metal the;v cold-statedue tothe uniform distribution in 'tlie' inetal'of-such of its constituents asthe ca-i'bids fof iron and of manganese ar'e'not lost hysuchreheating-Furthermore, I have found-thatzwhereas manganese steel in a heatedc'ondition, that.

' is, while haying temph'ratures above 300 C. may be, cut or machinedwith'tools'. of-high speed steel, providing that the metal hasbeenpreviously heat-treated and brought into a homogeneous condition, theInc Calif not previously heat-treated, that is so heated that thecarbidsof the metal have entered into solid solution in the grains or'crys'talscf-the steel,-'c'annot be machined without damage to the edges ofhighspeed steel tools.

.Accordingly, my invention comprises methods of -mac11ining previouslyheat treated manganese steel'j at temperatures above 300 0., and ofrestoring thereafter the uniform and tough condition of the 'metal whichhas been lost'by long heating of the metal at temperatures above-420 C.by suitably reheating and quenchin the metal; and methods of machiningsuch steel at temperatures substantially between 300 and 420 (3., meansof tools high speed steel. i

In the practice of invention, a cast or wrought blank, su'ch'as a blankshape for conversion into a cut gear, if not already heat-treated isfirst brought to a temperature of about 1000 C. and held at an equalized temperature, preferably within a range between'abcut 9'75 and 1025C until its carbide are in solution, and until the metal is so uniformlyrecrystallized that thereafter its texture will be adapted to thesubsequent cutting or machining. The blank may now be subjected to arough and rapid preliminary cutting to approximate the intended finishedshape or, may be rapidly cooled to below 420 C. and afterward heatedtotemperatures ranging from 300 C. to 1075 (3., and preferably to,-tempera tures between 300 C. and about 1000 C. depending on the depth ofthe requiredcut and the time which the cutting edge of the tool is toreinain in' contact .with the machining the cutting edge of themachiningv tool ofhigh spe'edsteelwill traverse the surface of cleavagewhile the manganese steel atthis. surface has a temperature between-300'C.and 420. C. To this end the shape to. be machined may be heatedat its surface in such manner'that at the moment of cutting at anypointthe surface of cleavage will have the desired machining tempera-' ture,that. is, within a range between 300 and 420 C. ;'-or the mass maybeheated throughout 'to any temperature between 300 and 420 C,,and then soquickly machined that thesurface ofcleava'ge will still have thetemperature within the range above specified. The finished shape is nowevenly cooled to atmospheric temperature to avoid distortion after themachining.

Having thusdescribed and explained the process wherein my invention.consists and having announced the discoveries whereupon 'it'depends, Iclaim and desire to secure by Letters Patent 1. The method of machiningblanks of manganese steel previously heat-treated to secure uniformityand homogeheousness of structure which comprises heatingthe blank toatemperature-between 300 C. and 1075"- C.';' machining it while in suchheated condition; and finally imparting qualities of toughness to theblank by water quenching, substantially as described.

i 2. In the machining of blanks of manganese steel previouslyheat-treated to secure uniformity and homogeneousness of structure andthen so rapidly cooled as to render the uniform state permanent, themethod which comprises heating the blank to 'a temperature between 300C. and 420 (1.; and machining the blank while in such heated condition,substantially as described.

3. In the machining of blanks of manganese steel previously heat-treatedto secure uniformity. and homogeneousness of structure the method whichcomprises heating the blank to a temperature between 300 C. and 120 (3.;such heated condition substantially as described.

at. In the machining of blanks of manga nese steel previouslyheat-treated to secure uniformity and homogeneousness of struc-.

ture the method which comprises machining the blank at a temperaturebetween 420 C. and 1075 0.; heating the blank to a temperature ofapproximately 1000 (l; and water quenching the machined blank, substantially as described.

- Signed at New York borough of Man hattan in the county of New York andState of New Yorkthis 27th day of December A. D. 1911. I

l/VINFIELD S. POTTER. WVitnesses:

R. N. FLINT, H, M. WHITE.

and machining the blank while in

